1. Field of the Invention
This invention relates to an evaporator for use in an air conditioner system. More particularly, this invention relates to a so-called louver fin type evaporator.
2. Description of Prior Art
Generally, a louver fin type evaporator 1 which is used in an automotive air conditioner system has its core part formed, as illustrated in FIG. 1, by using corrugated fins as its heat transfer fins 2, zigzagging a profile tube 3 in such a manner that straight portions thereof run parallelly to one another, and soldering the aforementioned corrugated fins 2 to the opposed outer surfaces of the parallel straight portions of the profile tube 3. The opposite ends of the profile tube 3 are connected to a coolant inlet tube 4 and a coolant outlet tube 5 respectively.
The heat transfer fins 2 of this evaporator 1 are formed by cutting a multiplicity of slats (louver boards R) in a substrate 6 and bending the cut slats in such a manner that, as viewed in a cross section cut in the direction of air current (namely, in the direction perpendicular to the surface of this sheet with respect to the diagram of FIG. 1), a first louver group R.sub.1 is sloped downwardly, a second louver group R.sub.2 upwardly, a third louver group R.sub.3 downwardly, and so on respectively relative to the direction of air current as illustrated in FIG. 2 (U.S. Pat. Nos. 3,993,125 and 3,003,749, Japanese Patent Open No. SHO 50(1975)-74245, Japanese Patent Publication No. SHO 52 (1977)-27852, and Japanese Utility Model Open Nos. SHO 52 (1977)-59995 and SHO 54(1979)-181,368.
The question as to how such louver boards R constituting the corrugated fins should be sloped relative to the direction of air current to make the most of the performance of the heat exchanger has been studied very little to date. Even in the assemblage of the aforementioned evaporator 1, the corrugated fins as a whole are completed by simply inserting numerous pieces between the opposed outer surfaces of the parallel straight portion of the profile tube 3. While these louver boards R are so set up during the assemblage, no due attention is paid to exactly regulating the directions in which the louver groups are to be sloped.
Only because this evaporator 1 is destined to give rise to water condensate, the behavior of water drops resulting from the condensation has been analyzed dynamically with a view to developing a measure to prevent such water drops from being blown away by the air current (Japanese Utility Model Open No. SHO 54(1979)-181368).
The outcome of this dynamic analysis is an invention which relates to downwardly sloping, relative to the direction of air current, the most downstream louver group R.sub.3 which is most liable to seize water condensate between adjacent louver boards R. In this particular region, the forced fall of water condensate by the air current and the spontaneous fall of water condensate by the gravitational attraction offset enough for water drops to fall down smoothly.
The measure to preclude possible drift of water condensate in the air current within the evaporator, however, cannot be devised successfully by mere dynamic analysis of the external forces exerted on water drops. The water condensate, on exposure to the air current, is caused to flow along louver boards or even heat transfer fins. The portion in which the water condensate occurs and stagnates is a kind of tunnel enclosed on all sides with walls. Due consideration paid exclusively to gravitational attraction and expelling force of air current cannot be sufficient for thorough elucidation of the behavior of water drops in question.